This application is based upon and claims the benefit of Japanese Patent Applications No. 2000-243278 filed on Aug. 10, 2000, No. 2000-243279 filed on Aug. 10, 2000, No. 2000-243280 filed on Aug. 10, 2000, and No. 2000-243281 filed on Aug. 10, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
This invention relates to a semiconductor device having an electronic part that is mounted on and electrically connected to a substrate through a bonding wire and sealed together with the bonding wire.
2. Description of the Related Art
FIGS. 1 and 2 show a semiconductor device 200. In the semiconductor device 200, referring to FIG. 1, several ceramic substrates 204 are disposed approximately perpendicularly to a motherboard 202 on which various electronic parts 201 are mounted. Referring to FIG. 2, electronic parts 203 are mounted on a surface of each ceramic substrate 204, and the other surface thereof is bonded to a radiation member 205 by silicone system conditioner 210. An end of a connection terminal (clip terminal) 206 is bonded to an edge portion of each ceramic substrate 204 at a side of the motherboard 202. The connection terminal 206 is positioned via an array board 207, and the other end of the connection terminal 206 is electrically connected to the motherboard 201.
These parts 201 to 207 are housed in a case 208. The electronic parts 203 mounted on the ceramic substrates 204, are surrounded by a protruding portion 208a of the case 208 to be protected from external environment and to improve radiation properties thereof, and are sealed with resin 209 or the like.
In the semiconductor device 200 having the above-described structure, as shown in FIGS. 1 and 2, in order to improve the efficiency in manufacturing steps, the several ceramic substrates 204 are disposed on the identical surface of the support member (radiation member) 205, and all the electronic parts 203 are sealed with the resin 209 together. In general, silicone rubber or the like having high viscosity is used as the resin 209 because it is easy to handle.
However, in a case where the electronic parts 203 are electrically connected to the ceramic substrates 204 by fine bonding wires, there is a possibility that the bonding wires are broken or strained when the resin is poured. The strained wires may be broken due to the resin 209 that strains when the semiconductor device 200 undergoes thermal shock cycles. Especially, when each diameter of the wires is smaller than 150 xcexcm, this problem becomes prominent. In view of this point, silicone gel having low viscosity is preferred to seal the electronic parts 203.
However, when all the electronic parts 203 are sealed by silicone gel together, the following problems arise. First, because gal having low viscosity is disposed in a large volume (area), the gel may oscillate to break the bonding wires when the semiconductor device 200 oscillates. Further, when gel is injected, bubbles are liable to be produced in the injected gel at step portions or the like between the ceramic substrates 204 and the radiation member 205. If bubbles exist around the fine bonding wires, the bubbles strain the gel during the thermal shock cycles of the semiconductor device 200, and as a result, the strained gel can strain the bonding wires.
The present invention has been made in view of the above problems. An object of the present invention is to provide a semiconductor device capable of restricting strain and breakage of a bonding wire wire-bonded to an electronic part sealed therein.
According to a first aspect of the present invention, a plurality of substrates are attached to a support member, and an electronic part is mounted on one of the substrates and electrically connected to the one through a bonding wire. An enclosing member covers the electronic part and the bonding wire, and a sealing material fills the enclosing member for sealing the electronic part and the bonding wire. Preferably, the enclosing member is composed of a plurality of enclosing members each of which is attached to a corresponding one of the plurality of substrates.
Because the electronic part and the bonding wire is covered with the enclosing member on every substrate, a volume of the sealing material filling the enclosing member is reduced, resulting in reduced amplitude of the sealing material. Further, bubbles are less liable to be produced in the sealing material. As a result, the bonding wire is restrained from being strained or broken by bubbles and the like.
According to a second aspect of the present invention, an electronic part is mounted on a substrate, and is electrically connected to the substrate through a bonding wire. An enclosing member covers the electronic part and the bonding wire, and a sealing material fills the enclosing member for sealing the electronic part and the bonding wire. The enclosing member has a first opening portion for injecting the sealing material into the enclosing member and a second opening portion for releasing gas from the enclosing member when the sealing material is injected. Preferably, the second opening portion has a width equal to or larger than that of the first opening portion. In this case, because gas can be released from the sealing material easily, bubbles produced in the sealing material can be reduced.
According to a third aspect of the present invention, an electronic part is disposed on a substrate, and a sealing member covering and sealing an electronic part and a bonding wire has a height equal to or smaller than 5 mm in a normal direction of the substrate, a shape that is contained in a rectangle having a long side of 60 mm and a short side of 20 mm, and a penetration in a range of 40 to 170 mm/10 (Refer to Japanese Industrial Standard (JIS), K 2220). The height of the sealing member is preferably equal to or smaller than 3 mm, and more preferably equal to or smaller than 2.5 mm. As a result, the oscillation of the sealing member can be suppressed, thereby preventing strain and breakage of the bonding wire.
According to a fourth aspect of the present invention, a method for manufacturing a semiconductor device comprises disposing an electronic part on a substrate; soldering a solder connecting member to the substrate; washing the substrate in a first solvent for removing flux from the substrate while keeping a concentration of the flux in the first solvent being 0.4 wt % or less, the flux being used when the solder connecting member is soldered; washing the substrate in a second solvent for removing the first solvent from the substrate, while keeping a concentration of the first solvent dissolved in the second solvent being 0.8 wt % or less; and electrically connecting the electronic part to the substrate by wire bonding using a bonding wire. In this method, because washing residues can be removed effectively, the connecting property of the bonding wire can be improved.